1. Field of the Invention
The present invention generally relates to an image correction circuit and method. More particularly, the present invention relates to a flat panel display and the image correction circuit and method of the same.
2. Description of Related Art
As the multi-media technology advances, the requirement of display device increases day by day. Therefore, manufacturers in this field have spent a lot of efforts to develop display devices. Conventionally, due to its high display quality and well-developed technology, cathode ray tube (CRT) display has been dominated the market. In recent years, however, liquid crystal display (LCD) has been gradually accepted by users because of the advantages of light weight, thin thickness, high definition, small size, low power consumption and radiation free. Therefore, LCD gradually replaces the conventional CRT display and becomes the main stream of display device in the market of display device.
In general, the LCD shows images by using specific driving voltages to control tilt angles of liquid crystal molecules, wherein the value of driving voltages are decided by corresponding image signal (e.g., digital signal). However, the relationship between image signals (or the value of the driving voltage) and the tilt angles of the liquid crystal (or even the transmittance of the pixel) is not linear. Therefore, a gamma correction circuit is required for adjusting the driving voltage generated from the image signals so that the relationship between the driving voltage generated from the image signals and tilt angles of the liquid crystal (or even the transmittance of the pixel) can be linear.
At present, gamma voltages of display device are provided by using resistor stream to divide reference voltages. In a conventional LCD, the resister stream is generally disposed in a printed circuit board (PCB) outside the display device. However, in the new generation electronic products such as driving chip of mobile phones or dynamic gamma correction system, the resister stream for generating the gamma voltage is disposed in digital to analog conversion circuit. In addition, the resister stream is built in the integrated circuits of the digital to analog conversion circuit.
FIG. 1 is a circuit block diagram of a conventional gamma voltage generator. Referring to FIG. 1, a gamma voltage generator 100 mainly includes a resister stream 102, a plurality of selectors 104 and a voltage dividing unit 16. The resister stream 102 is constructed by a plurality of resistors connected in series. In addition, the resister stream 102 may be built in an integrated circuit (not shown). The selector 104 is connected between the resister stream 102 and the voltage dividing unit 106. The selector 104 may be, for example, controlled, by using a 3 bit control code. Therefore, each selector 104 can output 8 different voltage values.
Referring to FIG. 1, in a conventional 64 level LCD, for example, each selector 104 can output voltages V0, V1, V8, V20, V43, V55, V62 and V63 to a voltage dividing unit 106 with reference of the resister stream 102 according to the stored control code. In addition, the voltage dividing unit 106 can generate all the 64 gamma voltages V0, V1, V2, V3, . . . , V8, V9, V10, . . . , V20, V21, . . . , V55, V56, V57, . . . , V62 and V63 by dividing received voltages.
Use a 256 level LCD for example, voltage difference between each level is about 20 mV. However, the voltage difference between each level of a 1024 level LCD will be further smaller. Therefore, it is very important to stabilize the gamma voltage of the LCD in order to maintain the image quality of the LCD.
However, when an integrated circuit is operated under a high temperature circumstance or is operated for a long time that the working temperature increases, resistance of each resistor of the resister stream 102 built in the integrated circuit may be shifted. As a result, the gamma voltages outputted from the gamma voltage generator 100 at high temperature may be different from the predetermined gamma voltages at room temperature that image quality of the LCD becomes poor.